This invention relates to a process and a device for adding a controlled dose of fluid to the eye. Conventional eye drops are difficult to use even for experienced patients. They are more problematic for children, the elderly, patients with impaired motor skills, and caregivers. Patients risk improper dosing, contamination of the eye dropper container, expensive waste due to spillage, and injury to the eyes from contact with the dropper bottle. These factors contribute to poor compliance. In addition, preservatives are added to the drops to provide medicine stability and reduce microbial contamination. These preservatives are known to cause morphological changes to the cornea, conjunctiva, and surrounding areas, which lead to irritation, stinging, burning, epiphora, hyperemia, keratitis, allergic and immune response, and scarring (1).
Subsequent reflex tearing leads to dilution of the medication, which can further alter pharmacodynamics. The quantity and concentration of the drug from conventional eye drops must be increased in order to account for the decreased bioavailability due to reflex tearing and the biophysiologic dynamics of the eye's structure. At least 80% of the drop is lost from excess tearing, spillage due to overflow from the eye's cul de sac, and rapid drainage through the nasolacrimal duct which increases the risk of systemic side effects (2). The eye has a tear turnover rate of 16% per minute which doubles after using conventional eye drops (3). In order to reach the aqueous humor at measurable levels, high concentrations of a drug are needed for one drop to be effective since only 3% of conventional eye drops penetrate the cornea (4).
New delivery systems include solutions, suspensions, sprays, gels, inserts, emulsions, mucoadhesives, collagen shields, and contact lenses. These are in addition to devices designed to facilitate the instillation of a drop to the eye. Although these methods are relatively safe, they have not fully addressed the main problems associated with drop delivery. In addition, they have not been implemented on a large scale (5).
What is needed is a new method and device that overcomes the basic challenges of the current eye dropper system which are:
1. Gravity.
2. Reduced bioavailability due to reflex tearing, eye drop spillover, and eye drop splash-back.
3. Difficult physical manipulation of the eye dropper bottle system by patients and caregivers.
4. Psychological apprehension of the eye drop instillation process.
5. Eye drop preservation process.